<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        .box1 {
            width: 200px;
            height: 200px;
            background-color: orange;
            opacity: 0.5;
        }
    </style>
</head>
<body>

    <div class="box1"></div>
    
</body>
</html>